This invention relates to a combustion apparatus wherein the formation of nitrogen oxides (hereinafter referred to as NO.sub.x) and the occurrence of combustion oscillation due to the combustion of a fuel are repressed.
As a measure to repress NO.sub.x formation, there has been known a two-stage combustion method which is based on a principle of burning, the fuel in a condition of deficient air supply to produce a reducing atmosphere. This two-stage combustion method represses the occurrence of NO.sub.x by either causing the NO.sub.x resulting from the combustion to be reduced into N.sub.2 in a reducing atmosphere or burning the fuel in a reducing atmosphere thereby enabling the N component of the fuel to be decomposed into N.sub.2 without being oxidized. To produce the reducing atmosphere in this two-stage combustion method, the air supply for the primary combustion is required to be maintained in a state of deficiency. When the air supply for the primary combustion is decreased below a certain level, there ensues oscillatory combustion.
This phenomenon can be presumed to occur because the supply of heat to the primary combustion zone is retarded due to the fact that when the air supply to this combustion zone is decreased the circulation of combustion gas is impaired and the velocity of reaction consequently lowered.